I also learnt my lesson when a Chipmunk did a loop about 50-100 metres off the port wing at the same level. I was in a C150 so I lost sight of the aircraft behind the wing for a second or two whilst I violently rolled the aircraft to remain visual. LARS said nothing, both aircraft transponder equipped and on same frequency. On speaking with the pilots they stated they got quite a fright when they saw me at the top!
This is one of many stories.